8800 Imatest Results

Review First Posted: 09/16/2004, Updated: 11/23/2004

Detailed analysis of the Nikon Coolpix 8800 images, from
Imatest(tm)

I've recently begun using Norman Koren's excellent "Imatest"
analysis program for quantitative, thoroughly objective analysis of digicam
test images. I highly commend it to our technically-oriented readers, as it's
far and away the best, most comprehensive analysis program I've found to date.
(And with an introductory price of only $59, it's hard to beat.)

My comments below are just brief observations of what I see in the Imatest
results. A full discussion of all the data Imatest produces is really beyond
the scope of this review: Visit the Imatest
web site for a full discussion of what the program measures, how it performs
its computations, and how to interpret its output.

Here's some of the results produced by Imatest for the Nikon Coolpix 8800:

Color Accuracy

Like most consumer/prosumer cameras, and even many SLRs, the Coolpix 8800
tends to oversaturate colors somewhat. The 8800 differs though, in that it
doesn't oversaturate pure reds quite as much as most, but oversaturates strong
blues more than average. Bright greens are also quite strong. The overall
effect in its images isn't bad, but its colors do appear a bit more intense
than average. On average, color saturation of swatches on the MacBeth ColorChecker(tm)
chart are 116.8% of their ideal values. (An average oversaturation of 16.8%.)

Color Analysis

These images show the color behavior of the 8800 directly. In each color swatch,
the outer perimeter shows the color as actually captured by the camera, the
inner square shows the color after correcting for the luminance of the photographed
chart (as determined by a 2nd-order curve fit to the values of the gray swatches),
and the small rectangle inside the inner square shows what the color should
actually be, based on perfect rendering to the sRGB color spacer. From this
plot, we can see that the 8800 not only boosts saturation somewhat, but renders
highly-saturated colors brighter than they are in real life. As noted above,
the net result in its photos isn't unappealing (depending of course on your
tastes), but there's no question that its colors are a fair bit brighter than
average. (It's interesting to note though, that less-saturated colors are rendered
much more accurately. This helps the camera do a good job on skin tones, not
over-emphasizing reds or yellows as do some cameras with "hot" color
rendering.)

Gray Patch Tone and Noise Analysis

There's a lot in this particular graph, a lot more than I have room to go into
here. Bottom line, the Coolpix 8800's noise levels are quite lot at ISO 50,
with significant high-frequency content, which gives the noise a very fine-grained
characteristic that minimizes its visual impact. (You can see the high-frequency
nature of its noise by the gentle slope on the Noise Spectrum plot above.)

I don't usually bother showing a second noise graph for the cameras I test,
but in the case of the 8800, I thought it would be instructive. At higher ISOs,
its noise develops a much coarser "grain" pattern, making it much
more objectionable. What's interesting here is that the Imatest Noise Spectrum
plot above shows this quite directly, with more of a bulge on the left (low
frequency) side of the graph, and a more rapid falloff on the right (high frequency)
side.

This chart compares the 8800's noise performance over a range of ISOs against
that of competing cameras. As you can see, the 8800 and Sony DSC-F828 have very
similar performance. The Olympus C-8080 and Konica Minolta DiMAGE A2 both show
lower noise magnitudes. What this plot doesn't show though, is how the
cameras are achieving their noise levels. In the case of the 8080 and A2, both
cameras use more aggressive noise-suppression processing than do the 8800 or
828. The result is that their noise levels are lower, but they lose more detail
in image areas with subtle contrast.

I'm sure some readers will raise their eyebrows at my inclusion of the Nikon
D70 SLR on the graph. Yes, I know that this isn't a camera that directly
competes with the Coolpix 8800. BUT, it's a camera that very likely will be
considered as an option by many people looking at the Coolpix 8800. These are
very different cameras, with very different feature sets, but one key area in
which they differ is noise performance. The larger physical size of the sensors
on digital SLRs greatly helps their noise performance, as can be seen here.
In going to a D70 (with the "kit" lens) over a Coolpix 8800, you lose
the anti-shake technology that's built into the 8800, the 10x zoom lens, video
recording capability, a little compactness, and a little resolution. What you
gain though, are much lower noise levels, much more responsive shooting,
high-ISO capability, and the ability to interchange lenses. A tough tradeoff,
but one that needs to be made being fully cognizant of all the pros and cons--including
noise performance.

Resolution Chart Test Results

The chart above shows consolidated results from spatial frequency response
measurements in both the horizontal and vertical axes. The "MTF 50"
numbers tend to correlate best with visual perceptions of sharpness, so those
are what I focus on here. The uncorrected resolution figures are 1431 line widths
per picture height in the horizontal direction (corresponding to the vertically-oriented
edge), and 1408 along the vertical axis (corresponding to the horizontally-oriented
edge), for a combined average of 1420 LW/PH. Correcting to a "standardized"
sharpening with a one-pixel radius increases this number slightly, to an average
of 1559 LW/PH, a very good number.

For the real techno-geeks, the two plots below show the actual edge response
of the 8800, for horizontal and vertical edge. What's interesting in these plots
is how restrained the 8800's default sharpening is, and how little it disturbs
the underlying image detail.